Hand driers usually consist of a housing containing a fan and a heater, usually powered by electricity. An air outlet or nozzle ejects a stream of heated air over the hands, usually from one end of the housing, or through a nozzle which can in many cases be swivelled around so that the air is directed to a desired location. Fresh air is usually inducted into the housing at a location remote from the air outlet. In this way the heated air is continuously dissipated into the ambient air in the room and its calorific values are lost, or in summer months simply add to the load on the air conditioning facilities in the building. The fresh air inducted is at ambient temperatures and must be rapidly warmed to the desired drying temperature. There is in effect a continuous demand for heat energy for the incoming air which is then immediately dissipated again. While it is true that such driers incorporate timers so that the actual duration of operation is cut off after the time has expired, there is none the less a considerable waste of energy. It also well known that persons may need to extend the timed operation, and simply repeatedly press the operating switch.
There is an additional disadvantage to conventional hand driers, in that the location of the air outlet is often so designed that the heated air flow stream spreads widely as it exits into the atmosphere, and much of the calorific value in the heated air stream never even reach the hands at all. Some designs have more efficient outlets so as to guide the air stream more narrowly, but in these cases the air stream may be so narrow that it impinges on only a portion of the hands and the user may have to move the hands so as to direct the air onto all areas of the skin. In all cases the direction of airflow is one way ie from the outlet towards the hands and out into the atmosphere. Thus the hands are dried only from one direction. The hands must be turned around and wiped over each other, as is well known. Unless this is done the hands will remain wet on the sides that do not face the air stream.
Clearly it is desirable to provide a hand drier which is both more efficient in its use of electrical energy, and in which the calorific value of the heated air is to some extent recovered by recycling the heated air, and in which the heated air stream is at the same time directed in such a manner as to dry all areas of the hands simultaneously, and quickly, and with a minimum of loss of heated air, and consequent loss of calories, to the atmosphere.